There's something so repressed, chilly and somehow hopeless about the postwar childhood that Ken Livingstone portrays in these memoirs that it is perhaps no surprise that from an early age he took to keeping a menagerie of cold-blooded creatures in his bedroom. At least he could exert some degree of power over them and need expect nothing but their presence in return.

Nor was much expected of Ken either, after he failed the 11-plus. He was discouraged from doing his homework, as it was perceived to be, for him at least, a waste of time. Isolated from other children, potty-trained by his grandmother by rubbing his face in his mess, deprived of parental touch, it is a wonder that he has survived as a normal functioning human being.

Ken has since found the emotional courage to shed many a tear as an adult. There are half a dozen occasions where he confesses to crying; and the suspicion is that there have been more. No wonder he says he found it liberating when later in his life men began to show their feelings in public. In this he differs from his London mayoral nemesis, Boris Johnson, who also experienced a challenging childhood, albeit in different ways. Both are flamboyant, arguably solipsistic characters, who find comfort and thrills in squiring women. But Johnson exerts a greater self-control. Livingstone admits to both hard graft and fear – he trembled so much during his first political speech he had to lean against a wall – whereas Johnson's aim is to dress up his success as effortless.

Yet it would be wrong to expect an emote-fest from Livingstone. He writes in the same monotone as his trademark nasal speaking voice, whether recounting the death of his Tory-supporting father (a loss that shook Ken badly despite, or perhaps because of, their distant early relationship) or the interminable 1970s municipal machinations of some Trotskyite faction – which may still enthrall him but is tedious for pretty much anyone else.

His obsessive interest in politics – perhaps it provided him with the family he wanted – is neatly illustrated by his insistence on dragging his mother and first wife, Christine, to a local housing committee meeting while on holiday in Connecticut. It certainly contributed to the bust-up of that marriage. And yet, while he claims that his own painful childhood memories put him off having his own blood family, he now has no fewer than three.

At 700 pages, the book is too long and the entire chapter on his youthful travels in Africa could have been excised without any great loss. But it is also often engaging. It is impossible to read the disproportionately virulent invective fired at him from his critics and not marvel that he was elected twice as Mayor of London and continues to be up for the fight. His refusal to accept when he has got it wrong plus a ruthless approach to opponents – casually dismissed as paedophiles, racists or incompetents – is also, on occasion, startling.

Charles Moore once described him as the only successful left-wing politician in Britain, and although the electoral tide is now against him he cannot yet be counted out. The newts and salamanders have been parked in the background in the lead-up to the 2012 mayoral elections. His new secret weapon is a warm-blooded, if flatulent, Andrex puppy called Coco.

Sonia Purnell is the author of the unofficial biography of Boris Johnson, Just Boris, published by Aurum Press, £20